By Mike Sokol
Welcome to my J.A.M. (Just Ask Mike) Session, a weekly column where I answer your basic electrical questions. If you’re a newbie who’s never plugged in a shore power cord (or ask – what’s a shore power cord?), or wonder why your daughter’s hair dryer keeps tripping the circuit breaker, this column is for you. Send your questions to Mike Sokol at mike (at) noshockzone.org with the subject line – JAM.
I’ve received several questions like this one in just the last week, so I think it’s a great JAM session. What do you do when your converter fails and the house batteries die?
I’m stuck at a campground and can’t get my hydraulic levelers to work or my slides to retract. Also the lights inside of the RV are really dim and my monitor panel says the battery is dead. How can that be since I’ve been plugged into shore power for days? – Stuck in Duck (NC)
Dear Stuck in Duck,
Okay, there’s one basic tool you should never leave without, and one extra gadget which I think would be very useful to carry with you. Yes, I know you all say I carry too much, but many times I’ve been 3,000 miles from home solo and needed to make things work. So this is how I make things work.
First of all, everyone who travels in an RV needs a basic Digital Meter. They’re just too useful for troubleshooting any RV electrical system and can save you a ton of time (and money) in the long run. I like the inexpensive manual ones from Southwire and Klein which you can get at any big box store for $20 or so. Here’s a Southwire 10030S which is a great choice. If you don’t know how to use one, I have a number of articles on RVtravel that go over the basics. So now is a good time to start with something like this one. Read about it using a meter to measure a 12-volt battery HERE.
Secondly, if you’re RV can’t be packed up to leave without battery power for the levelers and slides, then you should consider carrying a simple 10-amp battery charger for your tow vehicle. Even this $50 one from Harbor Freight looks like it should do the job. They will have sales on these for a low as $40, so it won’t break the bank.
But first you need to determine if your converter/charger has failed. The best way to know is simply measure the DC voltage across the battery with the shore power connected and the circuit breaker feeding the converter/charger turned on. Set the meter to the 20 volt DC range, and place the red meter probe on the positive battery terminal, and the black probe on the negative battery terminal. If the battery measures something over 14 volts, then the charger part of your converter is working and it’s likely not the problem. So something else must be wrong. However, if you’re reading mid to low 12 volts across your house battery, then your RV converter/charger is no longer charging the batteries and they’ve discharged so low you can’t run anything that needs significant power.
The key thing to remember is that a service call from an RV technician is going to be expensive and could take days to schedule. What you really need to do is get your RV batteries charged up so you can pull up your levelers, pull in your slides, and get on the road. Then you can troubleshoot the converter/charger at the leisure after you get home.
All you have to do is connect the red alligator clip to the 12-volt positive terminal on the battery (or batteries) and the black alligator clip to the negative terminal of the battery or batteries that’s connected to the RV chassis ground. It’s super simple with 12 volt batteries and only a little more complicated with a pair of 6 volt batteries in series.
A 10-amp charger should bring up a dead battery to half-charge in about 5 hours or so, maybe less. And that should easily be enough power to get your RV properly retracted for a homeward journey.
OK, everyone. Remember that electricity is a useful and powerful force, so we all need to pay attention to safety precautions while using it.
Let’s play safe out there….
Mike Sokol is an electrical and professional sound expert with 50+ years in the industry. His excellent book RV Electrical Safety is available at Amazon.com. For more info on Mike’s qualifications as an electrical expert, click here.
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